Shell is to sell off three oil and gas producing assets in the North Sea as the new chief executive's divestment gathers pace. The disposal of the Anasuria, Nelson and Sean platforms and production systems come at a sensitive political time when other energy bosses have signalled that the forthcoming referendum on Scottish independence is undermining the investment climate.

Shell was keen to deny that the move was influenced by politics, or that the Anglo-Dutch company was not committed to a UK North Sea sector where overall production has fallen by two thirds since 2000.

Glen Cayley, vice-president for Upstream Shell UK and Ireland said: "The UK is an important business region for Shell, and our investment strategy continues to focus on assets where we see an opportunity for growth using our world-class technological know-how."

He added: "We are talking to staff about the proposal to sell the assets in order to be as open as possible, whilst confirming our commitment to the North Sea."

But the pullback will increase nervousness both inside the industry and out. The UK Oil & Gas lobby group has warned the government that steps need to be taken if a steep decline in oil and gas output is to be reversed.

Meanwhile, Bob Dudley, chief executive of BP, last week gave the starkest warning yet that the business sector does not like the kind of political uncertainty created by the September referendum. Scottish politicians have made clear they would stake a claim to the vast bulk of Britain's oil and gas reserves in the event of a vote for independence.

• This article was amended on 14 February 2014. An earlier version appeared to suggest that Shell said it may not be committed to the UK North Sea sector. This has been corrected.